2'-Deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives, a process for the preparation of the derivatives and anti-tumor agents containing the derivatives

The present invention relates to 2'-Deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives, a process for the preparation of the derivatives and anti-tumor agents containing the derivatives as active ingredients thereof. More particularly, the present invention relates to new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives of the general formula: ##STR2## wherein R stands for an alkyl group, an alkoxy group or a halogen atom, m for zero or an integer of 1-3, and n for an integer of 1-14, with the proviso that when m is 2 or 3, R's may be the same or different and that when m is 2 and the adjacent two R's are alkoxy groups, the two alkyl moieties of the alkoxy groups may be combined to form together with the two adjacent oxa bridging members an alkylenedioxy group as a whole, a process for the preparation of the derivatives wherein a 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine is reacted with a benzoyl halide derivative, and anti-tumor agents containing the 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives as active ingredients thereof.

In the field of chemotherapy, the major public attention is now directed to the development of effective anti-tumor agents. Heretofore, various kinds of 5-fluorouridine derivatives have been developed as anti-tumor agents. However, all of these derivatives are quite unsatisfactory as they are either poor in the inherent anti-tumor activity or exhibit strong toxicity. 2'-Deoxy-5-fluorouridine (referred to hereinafter simply as FUDR) is already used as an anti-tumor agent but this compound is exceptionally high in toxicity for medication and has a narrower safety region. In addition, this compound is subject to a considerable limitations in actual therapeutic applications since the mode of administering this compound is limited only to intraarterial injection, or in other words, this compound cannot be administered orally [Physicians' Desk Reference, p. 1387 (1978)].

Heretofore, extensive researches have been made by C. Heidelberger et al. on the mechanism of anti-tumor activity of FUDR and a variety of studies have also been made by them to develop new FUDR derivatives which are devoid of such drawbacks and possess a high level of anti-tumor activity of chemical modification of FUDR. As a result of the studies 2'-deoxy-3',5'-di-O-acetyl-5-fluorouridine (referred to hereinafter simply as acetyl-FUDR) as one of the new chemically modified FUDR derivatives was found to possess such a property that this compound is hardly decomposed in living body, thus suggesting the possibility of oral administration [Cancer Research, 23, 49 et seq. (1963)]. As a result of experiments made on anti-tumor activity of the acetyl-FUDR, however, this compound is evaluated to be almost equivalent in anti-tumor activity to FUDR or rather poor in effectiveness [Biochem. Pharmacology, 14, 1605 et seq., (1965); Cancer Research, 23, 420 et seq. (1963)]. Thus, the acetyl-FUDR is still unsatisfactory as a practically effective anti-tumor agent.

A number of researches have thus been made on FUDR derivatives and results of the researches are summarized, for example, as a correlation between the chemical structure and the anti-tumor activity of FUDR and its derivatives in Cancer Research, 30, 1555-6 (1970).

In this reference, three enzymatic activities which were found to keys to the development of anti-tumor activity as a result of clarifying the mechanism of anti-tumor activity exhibited by FUDR are taken up as subjects and an explanatory diagram is given to show that positions and what structures of the FUDR molecule are necessary for exhibiting anti-tumor activity. In this reference, however, it is stated that the nitrogen atom in 3-position of the uracil (pyrimidine or pyrimidione) ring of FUDR should not be substituted.

3',5'-Dialkyl esters of FUDR are also reported as derivatives of FUDR but they are still unsatisfactory with respect to anti-tumor activity and toxicity [Biochem. Pharmacology, 14. 1605-1619 (1965), ibid. 15, 627-644 (1966)]. Recently, FUDR and acetyl-FUDR derivatives have been reported wherein the hydrogen atom bonded to the 3-nitrogen atom on the uracil ring is substituted by a specific aroyl group (UK Patent Appln. No. 2,025,401 published on Jan. 23, 1980 and European Patent Appln. No. 9,882 published on Apr. 16, 1980). However, further enhancement in anti-tumor activity is desired also in these compounds. Thus, there is a great demand for developing new FUDR derivatives which possess strong anti-tumor activity with weak toxicity and are suited for oral administration without the necessity of troublesome intraarterial or intravenous injection.

Accordingly, it is an object of the present invention to provide new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives of the general formula (I) possessing strong anti-tumor activity with a low level of toxicity.

It is another object of the present invention to provide a process for the preparation of the new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives of the general formula (I).

It is further object of the present invention to provide the use of the new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives of the general formula (I) as anti-tumor agents.

It is still another object of the present invention to provide anti-tumor agents containing the new compounds of the general formula (I) as active ingredient.

It is still further object of the present invention to provide anti-tumor agents useful for both injection and oral administration.

It is yet further object of the present invention to provide the use of the anti-tumor agents for chemotherapy of tumors.

Other objects, features and advantages of the present invention will become more fully apparent from the following description.

With a view to developing new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives possessing a high level of anti-tumor activity with weak toxicity, the present inventors have made extensive researches on new classes of 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives prepared from various 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridines.

As a result of the extensive researches, it has now surprisingly been found that the new compounds of the general formula (I) are superior in anti-tumor activity to the known similar compounds at an equivalent toxicity level. The present invention has been accomplished on the basis of the above finding.

In accordance with one embodiment of the present invention, there are provided new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives of the general formula: ##STR3## wherein R stands for an alkyl group, an alkoxy group or a halogen atom, m for zero or an integer of 1-3, and n for an integer of 1-14, with the proviso that when m is 2 or 3, R's may be the same or different and that when m is 2 and the adjacent two R's are alkoxy groups, the two alkyl moieties of the alkoxy groups may be combined to form together with the two adjacent oxa bridging members an alkylenedioxy group as a whole.

In the general formula (I), the benzoyl group introduced into 3-position of the uracil ring may be ring-substituted with up to 3(R) radicals which may be the same or different and each represent an alkyl group, an alkoxy group or a halogen atom. When R stands for an alkyl group, straight or branched chain C 1-20 alkyl groups are possible, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, n-octyl, n-decyl, n-dodecyl, n-hexadecyl and n-octadecyl. Illustrative of substituents wherein R is an alkoxy group are, for example, straight or branched chain C 1-20 alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentyloxy, n-hexyloxy, n-octyloxy, n-decyloxy, n-dodecyloxy, n-hexadecyloxy and n-octadecyloxy groups.

When two vicinal lower alkoxy groups exist as ring-substituents in the benzoyl group (R=a lower alkoxy group and m=2), the alkyl moieties of the two lower alkoxy groups may be combined to form an alkylene group. In this case, the two vicinal lower alkoxy groups form an alkylenedioxy group as a whole. Preferable examples of the alkylenedioxy group include methylenedioxy, ethylenedioxy and propylenedioxy groups.

Examples of substituted wherein R is a halogen atom include fluorine, chlorine, bromine and iodine atoms, with fluorine being preferred.

The hydroxy groups in the 3'- and 5'-positions of 2'-deoxy-5-fluorouridine are esterified with the same fatty acid of the formula CH 3 (CH 2 ) n COOH wherein n has the same meanings given above. The number n is preferably 1, 2, 5, 6, 10, 12 and 14. More precisely, preferred residues of fatty acids occupying the 3'- and 5'-positions are propionyl, butanoyl, heptanoyl, octanoyl, dodecanoyl, myristyl and palmitoyl groups.

Preferred compounds of the general formula (I) include:

3-benzoyl-2'-deoxy-3',5'-di-O-butanoyl or -dodecyl-5-fluorouridine,

3-(2,3 or 4-methylbenzoyl)-2'-deoxy-3',5'-di-O-propionyl or -butanoyl-5-fluorouridine,

3-(2,3 or 4-methylbenzoyl)-2'-deoxy-3',5'-di-O-octanoyl or -dodecyl-5-fluorouridine,

3-(2,3- or 3,4-dimethoxybenzoyl)-2'-deoxy-3',5'-propionyl or -butanoyl-5-fluorouridine,

3-(2,3 or 3,4-dimethoxybenzoyl)-2'-deoxy-3',5'-octanoyl or -dodecyl-5-fluorouridine,

3-(2,3- or 4-fluorobenzoyl)-2'-deoxy-3',5'-propionyl or -butanoyl-5-fluorouridine, and

3-(2,3 or 4-fluorobenzoyl)-2'-deoxy-3',5'-myristoyl or -palmitoyl-5-fluorouridine.

In accordance with another embodiment of the present invention, there is provided a process for the preparation of new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives of the general formula: ##STR4## wherein R stands for an alkyl group, an alkoxy group or a halogen atom, m for zero or an integer of 1-3, and n for an integer of 1-14, with the proviso that when m is 2 or 3, R's may be the same or different and that when m is 2 and the adjacent two R's are alkoxy groups, the two alkyl moieties of the alkoxy groups may be combined to form together with the two adjacent oxa bridging members an alkylenedioxy group as a whole, characterized by reacting a 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine of the general formula: ##STR5## wherein n has the meaning as given above, with a benzoyl halide of the general formula: ##STR6## wherein R and m have the same meanings as given above and Hal for a halogen atom.

In general, 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridines of the general formula (II) are known or can easily be prepared by acylating one molar proportion of FUDR with two molar proportion of the corresponding fatty acid preferably in the form of a reactive functional derivative. Benzoyl halides of the general formula (III) are generally known and easily commercially available or can be prepared in a manner known per se. The use of the corresponding chloride or bromide is preferable.

The benzoyl halide of the general formula (III) is preferably used in an amount of 1-3 molar proportion for the 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine of the general formula (II).

The reaction between the benzoyl halide of the general formula (III) and the 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine of the general formula (II), i.e. N-acylation reaction of the fluorouridine with the benzoyl halide, is carried out as a rule in the presence of an organic solvent which is inert to the N-acylation and affords a proper reaction temperature. Illustrative of the preferable organic solvent are aprotic solvents such as diethyl ether, dioxane, chloroform, ethyl acetate, acetonitrile, pyridine, dimethylformamide and dimethylsulfoxide.

The reaction is carried out normally in the presence of an acid-binding agent. The reaction of the present invention is usually promoted by neutralizing a hydrogen halide liberated on the N-acylation of the fluorouridine with the benzoyl halide. Thus, organic bases are generally used as the acid-binding agent. Preferred examples of the organic base include aliphatic tertiary amines such as triethylamine and the like lower trialkylamines and aromatic and heterocyclic tertiary amines such as N,N-dialkylanilines and pyridine which may be substituted by a lower alkyl group or groups. These organic bases are usually miscible with the organic solvent used as the reaction medium but are precipitated when combined with the hydrogen halide. Accordingly, these organic bases can easily be separated from the reaction mixture after completion of the reaction.

The organic base is used usually in an amount of 1-5 moles per mole of the benzoyl halide. As the organic bases per se may be used as the reaction medium, an excess amount of the organic bases, for example, in an amount of 5-20 molar proportion for the benzoyl halide may be used in place of a part or all of the reaction solvent.

The reaction is carried out within a wide range of reaction temperature, for example, under ice cooling or at a temperature up to the boiling point of the reaction solvent used. As a rule, the reaction time is within a period from 30 minutes to 12 hours. It is possible to shorten the reaction time by warming the reaction mixture at the final stage of the reaction.

After completion of the reaction, the end product can be obtained by subjecting the reaction mixture directly to concentration under reduced pressure or by first filtering the reaction mixture and then concentrating the filtrate under the reduced pressure, and finally recrystallizing the resultant residue or subjecting the residue to chromatography on silica gel. If necessary, the last-mentioned purification treatment by the aid of chromatographic operation or recrystallization may be repeated. When the end product is isolated as a viscous oily substance, it can be obtained as a solid or crystalline form by dissolving the oily substance in a small amount of dimethylsulfoxide and pouring the solution into water under vigorous agitation.

The products of the present invention possess high anti-tumor activity with weak toxicity as compared with the known similar FUDR derivatives. The anti-tumor activity and toxicity of the new compounds of this invention were evaluated according to the following tests.

(A) Pharmacological tests for measuring anti-tumor activity:

About 10,000,000 tumor cells of Sarcoma S-180 (successively incubated for several generations in peritoneal cavity of a male mouse of ICR strain) were transplanted subcutaneously into the inguinal region of 5 week-aged male mice of ICR strain. After the lapse of 24 hours, administration of the compounds of this invention started. The administration of the compounds of this invention was forcibly made orally once a day for 7 days. The body weight of each testing animal was measured every day just before the administration. The compounds of this invention were administered dissolved or suspended in polyethylene glycol 400 to each testing animal while polyethylene glycol 400 alone to a control group of the animals. In each case, the same volume of 0.1 ml/10 g (body weight) was administered to each animal. Although the exact doses of the compounds of this invention varied according to the sort of the particular compounds used, the doses were approximately within a range from 0.5 mg/kg to 120 mg/kg. The doses were graded into 3-12 ranks for each testing compound. At each rank, the compound of this invention was administered to a group consisting of 6 mice. As the control group, 18 mice were used.

On the 8th day from the transplantation of the tumor cells each mouse was put to death by bleeding under ether anesthesia. After the tumor tissue was excised, its weight was immediately measured and recorded. An average value of tumor weights in the treated group (referred to as T) for each test compound and for each dose and an average value of tumor weights in the control group (referred to as C) were calculated, respectively, to estimate a dose corresponding to T/C value of 0.70 or 0.50 for each test compound.

Concerning evaluation of the anti-tumor activity, a T/C value within the range of 0.70-0.51 is regarded to be slightly effective, while a value of less than 0.50 is regarded to be effective [Ohyo-Yakuri, 7, 1277-1292 (1973)]. Accordingly, the anti-tumor activity becomes stronger as the value indicating 0.70 or 0.50 in terms of T/C becomes smaller.

(B) Test for measuring toxicity:

Judging from the effects achieved by the compounds of this invention, toxicity values were measured according to the following method, taking accumulative toxicity into consideration.

Groups of 5 weeks old male mice of ICR strain were used for this test, each group consisting of 10 animals. Test compounds were forcibly administered orally once a day for 7 days. The body weight of each animal was measured every day just before the administration. The compounds of this invention were administered in the form dissolved or suspended in polyethylene glycol 400 to each testing animal in the same volume of 0.1 ml/10 g (body weight). Although the exact doses of the compounds of this invention varied according to the sort of the particular compounds used, the doses were approximately within a range from 10 mg/kg to 300 mg/kg. The doses were graded into 5 tanks for each testing compound. At each rank, the compound of this invention was administered to each group. On the 14th day from the completion of administration, the survival and death of the tested animals were judged and LD 10 values were calculated according to the Litchfield-Wilcoxon method.

The same tests as in the above (A) and (B) were performed, using the following known similar compounds:

A: 2'-Deoxy-3',5'-di-O-n-propionyl-5-fluorouridine

B: 2'-Deoxy-3',5'-di-O-n-butanoyl-5-fluorouridine

C: 2'-Deoxy-3',5'-di-O-n-heptanoyl-5-fluorouridine

D: 2'-Deoxy-3',5'-di-O-n-octanoyl-5-fluorouridine

E: 2'-Deoxy-3',5'-di-O-n-palmitoyl-5-fluorouridine

F: 3-(3,4-methylenedioxybenzoyl)-2'-deoxy-5-fluorouridine

G: 3-(3,4-methylenedioxybenzoyl)-2'-deoxy-3',5'-di-O-acetyl-5-fluorouridine

H: 5-Fluorouracil.

(C) Results of the Tests:

Results of the above Tests (A) and (B) and therapeutic indices calculated therefrom are shown in Table 1. The therapeutic indices were calculated according to the following equation: ##EQU1##

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Compound administered

Value indicating

Value indicating

LD.sub.10

Therapeutic

In General Formula, (R).sub.m

n T/C 0.70 (mg/Kg)

T/C 0.50 (mg/Kg)

(mg/Kg)

index

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Compound

2,3-Dimethoxy

1 25 44 90 2.05

of the

2,3-Dimethoxy

14 41 89 130 1.46

present

H (unsubstituted)

2 23 43 -- --

invention

3-Methyl 2 8 23 96 4.17

2-Methyl 5 4 11 -- --

2,3-Dimethoxy

5 6 18 33 1.83

3-Fluoro 5 1 8 24 3.00

2,3-Dimethoxy

6 6 20 36 1.80

3-Fluoro 6 7 21 41 1.95

known A 22 72 108 1.50

Compound

B 19 45 70 1.55

C 6 15 24 1.60

D 5 12 19 1.58

E 18 55 71 1.29

F 25 70 61 0.87

G 9 37 43 1.16

H 31 67 63 0.94

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As is evident from the results shown in Table 1, the compounds of the present invention exhibit strong anti-tumor activity at a relatively low level of toxicity, in comparison with the known similar compounds. Thus, the present invention apparently contributes to remarkable improvement in anti-tumor activity and in reduction of toxicity.

According to still another embodiment of the present invention, there is provided anti-tumor agents containing one or more of the new 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives of the general formula (I) as active ingredients.

In clinical chemotherapy, the compounds of this invention are preferably administered in a daily dose of 1-1000 mg. As a mode of administration, oral administration is preferably applied to the compounds of this invention but parenteral administration such as intravenous injection or intrarectal medication by means of a suppository is also applicable.

As pharmaceutical preparations suitable for oral administration, tablets, capsules (hard capsules and soft capsules), liquids and pills, each unit containing 0.5-500 mg of the compound of this invention as active ingredient, are possible. These preparations may contain, in addition to the active ingredient, other conventional auxiliary components such as milk sugar, corn starch, potato starch, various cane sugar esters of fatty acids, microcrystalline cellulose and polyethylene glycol 4000 as excipients; acacia, gelatine, hydroxypropylcellulose and potato starch as binders; magnesium stearate and talc as lubricants; carboxymethylcellulose calcium, potato starch and corn starch as disintegrating agents. Usual solubilizing agents and suspending agents may also be contained in the preparations, with polyethylene glycol 200-600 being particularly preferred. Examples for a base of suppositories include glycerol, cacao butter, glycerogelatine, polyethylene glycol, laurin and other materials usually employed for this purpose.

Besides the above mentioned additives, materials normally used as carriers for pharmaceutical preparations may also be contained in the anti-tumor agents of the present invention.

The present invention will now be illustrated in more detail by way of examples.